The Windward Turn Theory
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From: London
No, they both get to the destination, unless one it on the wrong flight.
Same as a ball that's facing sideways.
Next question.
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From: Boldly going where no split infinitive has gone before..
No not an identical force.
0 to 120 requires a tangential force
Making a 180 requires a centripetal force
In purely Newtonian terms force is force but for an aircraft, tangential and centripetal forces have quite different effects because it envolves rotating forces.
Ask a mathematician
0 to 120 requires a tangential force
Making a 180 requires a centripetal force
In purely Newtonian terms force is force but for an aircraft, tangential and centripetal forces have quite different effects because it envolves rotating forces.
Ask a mathematician
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From: London
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From: Boldly going where no split infinitive has gone before..
Yes, but can you have a groundspeed which is neither poitive nor negative?
A good starting point would be a definition of speed- I always just assumed it was the magnitude of velocity. You seem to have a different take on it.
A good starting point would be a definition of speed- I always just assumed it was the magnitude of velocity. You seem to have a different take on it.
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From: USA
It looks like you're moving backwards. It's what happens when you fly at 50 knots airspeed into a 60 knot headwind. Groundspeed is -10 knots.
Fortunately for the guy with the negative groundspeed, the destination is behind him.
Fortunately for the guy with the negative groundspeed, the destination is behind him.
Last edited by Vessbot; 6th August 2018 at 17:53.
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From: London
Thread Starter
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From: London
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From: Boldly going where no split infinitive has gone before..
Well, velocity is in relation to a frame of reference. If we are talking groundspeed, then relative to the ground.
The magnitude of velocity is the rate of change of position-m/s, km/hr, furlongs/ fortnight- it is how much your positionn has changed in the reference frame and how long the change took. I don't see how that can have a negative value.
The magnitude of velocity is the rate of change of position-m/s, km/hr, furlongs/ fortnight- it is how much your positionn has changed in the reference frame and how long the change took. I don't see how that can have a negative value.
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From: USA
It's embarrassing that the people on the correct side are chasing their tails on definitions and reference frames. Brercrow must be (justifiably) having a good laugh.
Yes, if you consider the aircraft a point object (like a ball) without a heading, then groundspeedvelocity can only have a direction and positive magnitude. But it's slightly more complicated than that, in that an aircraft has a set of body axes and everything is normally calculated relative to them as the direction component of the reference frame.
Again, before anyone got lost in the weeds of this thread, everyone would agree without a moment's hesitation of the trivial truth that in my scenario A, groundspeed is 90 initially and then 110. Not negative 110.
And again, imagine a dead calm day with no wind. Then, everything that is true about airspeed is true about groundspeed. If groundspeed is only positive, then airspeed is always positive, and therefore airplane should fly just the same in a tailslide as they do going forward. True or untrue?
Yes, if you consider the aircraft a point object (like a ball) without a heading, then ground
Again, before anyone got lost in the weeds of this thread, everyone would agree without a moment's hesitation of the trivial truth that in my scenario A, groundspeed is 90 initially and then 110. Not negative 110.
And again, imagine a dead calm day with no wind. Then, everything that is true about airspeed is true about groundspeed. If groundspeed is only positive, then airspeed is always positive, and therefore airplane should fly just the same in a tailslide as they do going forward. True or untrue?
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From: USA
Now it's your turn again to deal with the Cessna flying at 50 knots into a 60 knot headwind. What's his groundspeed?
Last edited by Vessbot; 6th August 2018 at 18:21.
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Well, velocity is in relation to a frame of reference. If we are talking groundspeed, then relative to the ground.
The magnitude of velocity is the rate of change of position-m/s, km/hr, furlongs/ fortnight- it is how much your positionn has changed in the reference frame and how long the change took. I don't see how that can have a negative value.
The magnitude of velocity is the rate of change of position-m/s, km/hr, furlongs/ fortnight- it is how much your positionn has changed in the reference frame and how long the change took. I don't see how that can have a negative value.
Last edited by Jet_Fan; 6th August 2018 at 18:21.
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From: Boldly going where no split infinitive has gone before..
Vesbot,
Yes we are just talking semantics.
The magnitude of the ground velocity of the Cessna is 10 knots, its direction being 180 degrees to its heading.
Its position over the grond is changing by 10 nautical miles every hour, and there is no such thing as a negative nautical mile.
I would maintain speed is a scalar quantity, and therefore has no direction. By invoking a positive or negative you are now actually defining a reference frame, and we are talking velocity, not speed.
I think our passengers actually demonstrate this- how can you change speed without accelerating?
Yes we are just talking semantics.
The magnitude of the ground velocity of the Cessna is 10 knots, its direction being 180 degrees to its heading.
Its position over the grond is changing by 10 nautical miles every hour, and there is no such thing as a negative nautical mile.
I would maintain speed is a scalar quantity, and therefore has no direction. By invoking a positive or negative you are now actually defining a reference frame, and we are talking velocity, not speed.
I think our passengers actually demonstrate this- how can you change speed without accelerating?
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From: London
Thread Starter
Joined: Sep 2015
Posts: 86
Likes: 9
From: London